Health Library

Conditions InDepth: Sinusitis

The sinuses are hollow areas in the skull that are arranged in pairs. Sinusitis occurs when the tissue lining the sinuses in the skull around the nose (the paranasal sinuses) becomes inflamed and infected. Sinusitis usually occurs with inflammation in the nasal passages (rhinitis). When they occur together, it is called rhinosinusitis. The infections are categorized by the length of time symptoms are present:

Acute rhinosinusitis—duration less than 4 weeks

Subacute rhinosinusitis—duration 4-12 weeks

Recurrent acute rhinosinusitis—four or more episodes per year with no symptoms between episodes

Acute sinusitis can be caused by viral infections, bacterial infections, or other causes.

Acute bacterial sinusitis may be caused by any number of bacteria, including:

Hemophilus influenzae

Streptococcus pneumoniae

Moraxella catarrhalis

Staphylococcus aureus

These are all bacteria that are often found in the nose and throat of healthy people and which cause other common conditions, such as
bronchitis
and
ear infections
.
A viral upper respiratory infection such as a cold often occurs just before developing a bacterial infection.

Certain other bacteria and fungi, such as
Aspergillus
, can be a cause of chronic sinusitis.

Sinusitis starts with swelling of the nasal and sinus passages. Tiny hairs called cilia usually move constantly to help shift mucus out of the sinuses. With sinusitis, these hairs stop working as well as they should. Both the swelling and lack of movement from cilia make it difficult for mucus to move out of the sinuses. This buildup of mucus and air create the pressure and pain associated with sinusitis. It also creates a nice place for bacteria and viruses to grow.

Sinusitis is an extremely common problem. In a given year, about 37 million Americans suffer from sinusitis.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

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